Provide a better error message if a podspec is found but cannot be parsed

CHANGELOG.md

@@ -12,6 +12,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 ##### Bug Fixes
 
+* Provide a better error message if a podspec is found but cannot be parsed.  
+  [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
+  [#6457](https://github.com/CocoaPods/CocoaPods/issues/6457)
+
 * Only share pod target xcscheme if present during validation.  
   [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
   [#6558](https://github.com/CocoaPods/CocoaPods/pull/6558)

lib/cocoapods/external_sources/abstract_external_source.rb

@@ -111,11 +111,15 @@ module Pod
         title = "Pre-downloading: `#{name}` #{description}"
         UI.titled_section(title,  :verbose_prefix => '-> ') do
           target = sandbox.pod_dir(name)
-          download_result = Downloader.download(download_request, target, :can_cache => can_cache)
+          begin
+            download_result = Downloader.download(download_request, target, :can_cache => can_cache)
+          rescue Pod::DSLError => e
+            raise Informative, "Failed to load '#{name}' podspec: #{e.message}"
+          rescue => _
+            raise Informative, "Unable to find a specification for '#{name}'."
+          end
           spec = download_result.spec
 
-          raise Informative, "Unable to find a specification for '#{name}'." unless spec
-
           store_podspec(sandbox, spec)
           sandbox.store_pre_downloaded_pod(name)
           sandbox.store_checkout_source(name, download_result.checkout_options)
@@ -147,17 +151,21 @@ module Pod
       # @return [void]
       #
       def store_podspec(sandbox, spec, json = false)
-        spec = case spec
-               when Pathname
-                 Specification.from_file(spec)
-               when String
-                 path = "#{name}.podspec"
-                 path << '.json' if json
-                 Specification.from_string(spec, path)
-               when Specification
-                 spec.dup
-               else
-                 raise "Unknown spec type: #{spec}"
+        begin
+          spec = case spec
+                 when Pathname
+                   Specification.from_file(spec)
+                 when String
+                   path = "#{name}.podspec"
+                   path << '.json' if json
+                   Specification.from_string(spec, path)
+                 when Specification
+                   spec.dup
+                 else
+                   raise "Unknown spec type: #{spec}"
+                 end
+        rescue Pod::DSLError => e
+          raise Informative, "Failed to load '#{name}' podspec: #{e.message}"
         end
         spec.defined_in_file = nil
         validate_podspec(spec)

lib/cocoapods/sandbox/podspec_finder.rb

@@ -12,13 +12,9 @@ module Pod
         @specs_by_name = {}
         spec_files = Pathname.glob(root + '{,*}.podspec{,.json}')
         spec_files.sort_by { |p| -p.to_path.split(File::SEPARATOR).size }.each do |file|
-          begin
-            spec = Specification.from_file(file)
-            spec.validate_cocoapods_version
-            @specs_by_name[spec.name] = spec
-          rescue => e
-            UI.warn "Unable to load a podspec from `#{file.basename}`, skipping:\n\n#{e}"
-          end
+          spec = Specification.from_file(file)
+          spec.validate_cocoapods_version
+          @specs_by_name[spec.name] = spec
         end
         @specs_by_name
       end

spec/unit/external_sources/abstract_external_source_spec.rb

@@ -26,6 +26,36 @@ module Pod
         @subject.fetch(config.sandbox)
         config.sandbox.specification('Reachability').name.should == 'Reachability'
       end
+
+      it 'raises appropriate error if a DSLError was raised' do
+        Downloader.stubs(:download).raises(Pod::DSLError.new('Invalid `Reachability.podspec` file:', 'some/path/to/podspec', Exception.new('Error Message')))
+        should.raise(Informative) do
+          e = @subject.send(:pre_download, config.sandbox)
+          e.message.should.include "Failed to load 'Reachability' podspec:"
+          e.message.should.include 'Invalid `Reachability.podspec` file:'
+        end
+      end
+
+      it 'raises appropriate error if a DSLError when storing a podspec from string' do
+        podspec = 'Pod::Spec.new do |s|; error; end'
+        should.raise(Informative) { @subject.send(:store_podspec, config.sandbox, podspec) }.
+            message.should.include "Invalid `Reachability.podspec` file: undefined local variable or method `error'"
+      end
+
+      it 'raises appropriate error if a DSLError when storing a podspec from file' do
+        podspec = 'Pod::Spec.new do |s|; error; end'
+        path = SpecHelper.temporary_directory + 'BananaLib.podspec'
+        File.open(path, 'w') { |f| f.write(podspec) }
+        should.raise(Informative) { @subject.send(:store_podspec, config.sandbox, path) }.
+            message.should.include "Invalid `BananaLib.podspec` file: undefined local variable or method `error'"
+      end
+
+      it 'raises a generic error if a podspec was not found' do
+        Downloader.stubs(:download).raises(Pod::Downloader::DownloaderError.new('Some generic exception'))
+        should.raise(Informative) do
+          @subject.send(:pre_download, config.sandbox).message.should == "Unable to find a specification for 'Reachability'."
+        end
+      end
     end
 
     #--------------------------------------#

spec/unit/sandbox/podspec_finder_spec.rb

@@ -15,12 +15,6 @@ module Pod
       @finder.podspecs.should.be.empty
     end
 
-    it "warns when a found podspec can't be parsed" do
-      @root.+('RestKit.podspec.json').open('w') { |f| f << '{]' }
-      @finder.podspecs.should.be.empty
-      UI.warnings.should.include "Unable to load a podspec from `RestKit.podspec.json`, skipping:\n\n"
-    end
-
     it 'ignores podspecs not in the root' do
       path = @root + 'Dir/RestKit.podspec.json'
       path.parent.mkpath